Yes, the osnaburg will need breaking in! Ironing does help. Some other break-in ideas: fold it up and sit on it like a pillow (or get your favorite couch potato to assist :-)), lie it on top of your fitted sheet and sleep on it, "braid" it (not really braiding but more like crochet--you could google for better instructions than I could give!), use it as a hammock or a swing (esp if you have older kids who can help). Also, if you're thinking of dyeing it, that might soften up new fabric, but it almost always stiffens up broken-in fabric, so that's something else to consider.